Moisture indicator



Patented Aug. 29, 1939 UNITED STATES PATENT OFFICE 2,171,363 MOISTURE INDICATOR Pennsylvania Application July 28, 1938, Serial No. 221,856

17 Claims.

My invention relates to indicators, and more specifically to indicators used to determine the amount of moisture present in paper or any fibrous material while in the process manufacture.

In the manufacture of paper, cloth or any other fibrous material, it becomes desirable to know the percentage of moisture present in order to produce a product having high qualities. Ac-

cording to the teachings of the prior art, various types of moisture content indicators have been proposed and devised but none have proven satisfactory. A number of principles have been utilized in operating indicators that are now availlli able. The most important among them are based on the following: Variation of power factor with changing moisture content; variation of surface friction with varying moisture content; and variation with moisture content of static my electrical charges generated by passing paper or cloth through a calender.

A further system utilizes the principle whereby the thermal conduction of moist air adjacent the paper affects the temperature of a heated wire that is suspended above the paper and thereby changes its resistance. All of the above-mentioned indicators are unsatisfactory in that their operation is also dependent upon characteristics other than the moisture content of paper, as for example, calender pressure, paper speed and atmospheric conditions.

Known indicators are based on constructions in which considerable frictional drag is present. An objection to this is that static electricity is generated in the paper in such proportions as to seriously interfere with-the indicator especially throwing the calibration ofi beyond satisfactory.

limits. I shall eliminate the errors caused by static interference and assure permanent calibration in my device.

According to my invention, I make use of the established fact that the resistance of paper varies with the moisture content. Briefly, my apparatus provides for means that indicate the rate of discharge of a condenser, which rate varies in inverse proportion to the moisture content of the fibrous material being tested.

It is, therefore, an object of my invention to provide an indicator adapted to show the moisture content of a fibrous material while in the process of manufacture.

Another object of my invention is to provide a simple and reliable means for determining. the moisture content of a fibrous substance, such as pap Still further, it is an object of my invention to provide a moisture indicator whose operation is dependent upon the rate of discharge of a condenser, which rate varies according to the resistance of the fibrous material. 5

Other objects and advantages of my invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing, in which the single figure represents a diagrammatic view of the appa- 10 ratus employed in practicing my invention.

Referring to the drawing in detail, I have shown my invention as comprising a rotatable member 3 formed of a pair of spaced circular disk-like insulators 5 and I rigidly connected 15 together at their centers by a rotatably mounted shaft 9. The disks 5 and I are adapted for rotation about a common axis and at their circumferences contact with a movable web II which is supported by a calender roll l2. I

On the periphery, or circumference, of each disk 5 and l, I mount a metallic bar or segment l3, preferably of copper. These segments are embedded in slots I5 provided for that purpose and fall in the same, or one plane radial to the 25 axis of rotation of the disks. A condenser H is connected between the two metallic bars l3-l3 and is mechanically secured thereto. A plurality of brush sets l9, 2|, 23, 25 and 21 are mounted to be in constant contact with the rim 3o portions of the rotatable member 3 and periodically contacting the segmental bars l3l3 which are kept in alignment by a key 29 in the shaft 9.

A battery 3| supplies a source of electrical current of constant potential for charging the 35 condenser II when the metallic segments l3-l3 are in contact with either the brushes l9 or 25. Likewise a pair of auxiliary condensers 33 and 35 are provided which are connected to different brush sets and are arranged to become charged 40 during predetermined positions of the metallic segments I3--I3. When the segments l3--l3 come in contact with brush set 21, a circuit is established from condenser I! to condenser 35. On the other hand, condenser 33 becomes charged 45 by the master condenser 11 when the metallic segments I3-I3 contact brush set 2|. The potential difference between the auxiliary condensers 33 and 35 is applied to the grid of an electron discharge device 3'l, such as a grid controlled tube, rendering the device 31 conductive. An ammeter 39 or any similar current indicating device may be inserted in the tube circuit to indicate the current flowing.

The apparatus I have illustrated comprises the essential features of my invention. The paper trate the position of the rotatable member 3 of my indicator with respect to the moving wb I I.

In the operation of my device, let it be assumed that the rotatable member 3 is rotating counterclockwise on the paper or web II, that is, the direction of the paper travel is assumed to be from left to right. When the metallic segments I3--I3 reach brush set I9, condenser I'I will be charged in proportion to the battery potential. When the segments reach the paper I I, the segments I3I3 cause the condenser I! to discharge at a rate which is inversely proportional to the moisture content of the paper II at this point, as the resistance of the paper I I is a direct function of the moisture content. When the segments I3--I3 contact brush set Z'L'the condenser I! will discharge into the auxiliary condenser 35, thus impressing a voltage across it, which will decrease if the moisture contentof the paper II increases.

It is necessary to compare the amount of discharge of the condenser I'I under these conditions with some standard. Hence, it becomes necessary to recharge the condenser II. This recharging takes place when the segments I3-I3 reach brush set and the value of the charge is again proportional to the voltage of battery 3|. Subsequently, when segments I3 reach brushes 23, condenser I'I discharges through a fixed resistor M, which is the standard of comparison. After the segments I3 have passed tion of the moisture content in'aweb while movbrushes 23, the remaining charge of the condenser I'I will then be transferred to a second auxiliary condenser 33 when the segments I3 reach brushes 2|. 7

During one revolution of the rotatable member 3, the net effect is that a charge is placed upon each of the two auxiliary condensers 33 and 35. The difference between the potentials across the auxiliary condensers 33 and 35 is applied to the grid 38 of a grid control amplifier tube 31. The current flowing through the tube 31, that isE-the principal electrodes of the tube, can thus be made to 'vary directly with the moisture content of the moving web I and can be measured by inserting a suitable ammeter 39 in the anode circuit. Of course, it, is, to be understood that the apparatus constituting my invention may be used to indicate various amounts of moisture present in the moving web I I simply by adjusting the resistance of the,resisto1 II.

For purposes of illustration I have shown a specific embodiment of my invention. However, it will be apparent to'thoseskilled in the art that changes and modifications can be made therein Without departing from the true spirit of my invention orthe scope of the appended claims.

I claim as my invention:

1. An indicator for the automatic determinaing during its course of manufacture, comprising,

in combination, rotatable means adapted to rotate on said movable Web and to contact the web at two spaced points, a capacitor arranged to be alternately charged and then discharged through said web between the spaced contact points,

tion of the moisture content in a web while moving during its course of manufacture, comprising, in combination, a pair of parellelly disposed rotatable members rigidly connected together, said rotatable members adapted to rotate on said movable web, a capacitor arranged to be alternately charged and then discharged through the web portion disposed between the points of contact of said members, whereby the magnitude of discharge is dependent upon the resistance of that portion of said movable web disposed direct 1y between the points of contact with said rotatable members and electronic means operable according to magnitude of discharge of said capacitor.

3. An indicator for the automatic determination of the moisture content in a web while moving during its course of manufacture comprising,

in combination, a pair of parallelly disposed rotatable members rigidly connected together and a master capacitor connected thereto, said members being disposed to make rotating contact with said movable web, a source of electric energy for charging said master capacitor when in predetermined positions with reference to said web, a pair of auxiliary capacitors arranged to be charged at different predetermined positions of said rotatable members with reference to said web, and electronic means responsive to the difference in the charges on said auxiliary capacitors,

4. An indicator for the automatic determination of the moisture content in a web while moving during its course of manufacture comprising, in combination, a pair of displaced rotatable membersrigidly connected together, each of said members having a notch in the periphery thereof, said notches falling substantially in the same radial plane, a metallic filling and a master capacitor connected therebetween, a plurality of brushes spaced about the periphery of said rotatablemembers, current means for charging said master capacitor in predetermined positions of said roatable memberswith reference to said web, a pair of auxiliary capacitors charged by said master capacitor at other predetermined positions of said rotatable members and electronic means responsive to the difference in the charges between said auxiliary capacitors.

5. In a moisture indicator comprising, in combination, a rotatable member adapted to rotate on a movable web, said rotatable member formed of a plurality of spaced disk-like insulators rigidly connected together at their central portions, a

.metallic segment at the periphery of each of said disk-like insulators, a master condenser connected between said insulators at said segments, a plurality of brushes spaced about the periphery of-said insulators, current means for periodically charging said master condenser, a pair of auxiliary' condensers connected so as to be periodical- 1y charged therefrom and electronic means responsive to the net potential difference between said auxiliary condensers.

6. In an indicator for the automatic determination of the moisture content in a web while moving during its course of manufacture, comprising, in combination, a rotatable member adapted .to rotate on said movable web and to contact the web at a pair of special points, a capacitor, 2. source of constant potential direct current energy, means for sequentially charging said capacitor from said source of direct current energy and then discharging said capacitor through the web portion disposed between the special contact points, whereby the rate of discharge is a Ill) function of the resistance of that portion of said movable web disposed directly. between the points of contact with said rotatable member and electronic means responsive to the operation of said capacitor.

7. An indicator for the automatic determination of the moisture content in a web while moving during its course of manufacture, comprising, in combination, a pair of insulated disks, a metallic segment on a portion of the circumference of each of said disks, a master capacitor connected between said metal segments, a plurality of pairs of brushes, said metal segments engageable with a different pair of said brushes upon rotation of said disks, a source of electrical current for energizing said master capacitor, a pair of auxiliary capacitors arranged to be charged by said master capacitor, each of said auxiliary capacitors in said pair operatively connected to a different group of said pairs of brushes and electronicmeans operated by the potential difference between said auxiliary capacitors.

8. An indicator for the automatic determination of the moisture content in a web while moving during its course of manufacture, comprising,

in combination, a pair of spaced disk-like insulators rigidly connected together at their central portion, a metallic segment on the circumference of each of said disks, a main capacitor connected between said segments, a plurality of brushes mounted to be in contact with the periphery of said disks, a source of electric energy for charging said main capacitor at predetermined positions of said metallic segments with reference to said web, auxiliary capacitors charged by said main capacitors, the rate of discharge of said main capacitor depending upon the resistance of the web at points of contact with said metallic segments and electronic means operated by the potential difference between said auxiliary capacitors.

9. A moisture indicator for determining the per cent of the moisture content of a moving web incuding a rotatable member positioned above said moving web and disposed to contact the web at two special points, a master condenser rotatable with said member, auxiliary condenser, means for charging said master condenser each time said member is in a given angular position, means for discharging saidmaster condenser into the auxiliary' condenser each time said member is in a given other angular position, and electronic means responsive to the electrostatic charge difference between said auxiliary condenser and the master condenser.

10. An indicator for the automatic determination of the moisture. content of a moving web, comprising, in combination, a rotatable member having conductor segments on the periphery thereof, said conductor segments thus being engageable with different sections of said web during rotation, a. master condenser rotatable with said member and connected to said segments, means for subjecting said segments to a potential to charge the master condenser each time the segments are not in contact with the web, and whereby the master condenser through the web each time the rotatable member is in such positionthat the contact segments contact the web, an auxiliary condenser means chargeable by the residual charge of said master condenser after having been subjected to a discharge through the web, and electronic means connectible to said auxiliary condensers to be energized in proportion to said residual charge;

discharges 11. A moisture indicator for a web manufacturing machine, in combination, a condenser, means for repeatedly charging said condenser to a given value of charge, means for alternately discharging said condenser, through an impedance and through a given length of the web being manufactured and means responsive to the difference between the residual charges on the condenser after each of the alternate discharges of said condenser.

12. A moisture indicator for a web manufacturing machine, in combination, a capacitor, means for charging said capacitor a given amount, means for discharging said capacitor through a given length of said web material and means for measuring the residual charge on said condenser.

13. A moisture indicator for a web comprising, in combination, a main capacitor, means for charging the main capacitor a given amount, means for discharging said capacitor through a given length of said web, a second capacitor, means for subjecting the second capacitor to the residual charge of the main capacitor after itsdischarge through the given length of said web, means for charging the main capacitor a given amount, a standard discharge circuit, means for discharging the main capacitor through said standard discharge circuit, a third capacitor, means for subjecting the third capacitor tothe second residual charge of the main capacitor after its discharge through the standard discharge circuit, and means responsive to the difference in the residual charging effect on the second and third capacitors.

14. In an electrical system for indicating the magnitude of a physical quantity, comprising, in combination, a, pair of spaced electric currentconducting members, a main condenser having its terminal connected to said members, a source of direct current, discharging means for discharging said condenser as a function of the physical quantity to be determined, measuring means for measuring the residual charge on said wondenser, and means for moving said members,

first, in contact with said source of direct current to charge the condenser to a givencharge, second, in contact with said discharging means, and, third, in contact with said measuring mean to determine the residual charge.

15. In an electrical system for indicating the magnitude of a physical quantity, comprising, in combination, a pair of spaced electric currentconducting members, a main condenser having its terminal connected to said members, a source of direct current, discharging means for discharging said condenser as a function of the physical quantity to be determined, measuring means for measuring the residual charge on said condenser, means for moving said members, first, in contact with said source of direct current to charge the condenser to a given charge, second, in contact with said discharging means, and, third, in contact with said measuring means to determine the residual charge, said measuring means comprising a capacitor adapted to be charged by the residual charge of said condenser, an electronic device controlled as a function of the charge on said capacitor, and means operated by the electronic means.

16. In an electrical system for indicating the magnitude of a physical quantity, comprising, in

combination, a pair of spaced discs of insulating ripheries of each of said discs and each extending over a portion only of said peripheries, a capacitor connected across said segments, a pair of brushes adapted to simultaneously contact said discs, a source of electric energy connected to said brushes thus adapted to charge the capacitor each time the brushes simultaneously contact said segments, a discharge circuit having electrical characteristics determined by the physical quantity to be determined, a second pair of brushes adapted to simultaneously contact the respective-peripheries of said discs when said segments are not in contact with the first pair of brushes, said second pair of brushes being connected to said discharge circuit, whereby said capacitor is discharged as a function of the physi cal quantity to be determined when said second pair of brushes are contacting said segments. a third pair of brushes adapted to simultaneously contact said segments when not in contact with the first two pairs of brushes, and measuring means connected to said third pair oi! brushesadapted to determine the residual charge on said capacitor.

17.. In an electrical system for indicating the magnitude of a physical quantity, comprising, in combination, a pair of spaced discs of insulating material, means for synchronously rotating said discs, conducting segments mounted in 30 the peripheries of each of said discs and each extending over a portion only of said peripheries, a capacitor connected across said segments, a pair of brushes adapted to simultaneously contact said discs, 9, source of electric energy connected to said brushes thus adapted to charge the capacitor each time the brushes simultaneously contact said segments, a discharge circuit having electrical characteristics determined by the physical quantity to be determined, a second pair of brushes adapted to simultaneously contact the respective peripheries of said discs when said segments are not in contact with the first pair of brushes, said second pair of brushes being connected to said discharge circuit, whereby said capacitor is discharged as a function of the physical quantity to be determined when said second pair of brushes are contacting said segments, 2. third pair of brushes adapted to simultaneously contact said segments when not in contact with the first two pairs of brushes, measuring means connected to said third pair of brushes adapted to determine the residual charge on said capacitor, said measuring means comprising a second capacitor adapted to be charged by the residual charge, electronic means controlled by the potential of the second capacitor, and electric apparatus responsive to the current variations of said electronic means.

FINN H. GULLIKSEN. 

